Underwater oil well completion



Oct. 17, 1961 D. c. KOFAHL 3,004,602

UNDERWATER on. WELL COMPLETION Filed Nov. 5, 1956 2 Sheets-Sheet 1 FIG. 1.

fiflV/O C. 8050 44 INVENTOR.

1951 D. c. KOFAHL 3, 04,602

UNDERWATER OIL WELL COMPLETION Filed Nov. 5, 1956 2 Sheets-Sheet 2 04140 6. 0 4,444. INVENTOR.

BY i a FIG. 2 54 aired rates This invention relates to a method and apparatus for completion of underwater wells such as oil wells, gas wells and the like. This invention finds particular usefulness in connection with the safe completion of a producing oil well beneath the ocean surface.

Among the general objects of this invention are to safely produce an oil or gas well without incurring the expense of a structural platform where the water depth is so great as to make such platforms prohibitively expensive. Another object is to avoid unsightly well heads and related production equipment projecting above the water surface in regions adjacent to recreational beaches, yacht harbors, etc. Another general object is to eliminate navigational hazards caused by oil well installation in the open sea.

A more particular object is to provide a method of well completion which involves landing a casing string and a tubing string on well head structure at the ocean floor and then providing an enclosure for at least a portion of the well head structure to prevent escape of well fluids into the sea. Another more particular object is to provide well completion apparatus including a casing head and a tubing head located at the ocean floor in a submerged position and wherein blowout preventers are mounted above the tubing head during the drilling operation. Other and more detailed objects and advantages will appear hereinafter.

In the drawings: 1

FIGURE 1 is a side elevation partly in section and partly broken away showing a preferred form of apparatus for use in connection with this invention.

FIGURE 2 is a view similar to FIGURE 1 showing the blowout preventers removed and a housing or enclosure installed about a portion of the well head assembly.

Referring to the drawings, the well head structuregenerally designated includes a casing head 11, a tubing head 12 and a series of blowout preventers 13, 14 and 15. These devices may be of conventional form except as described in detail herein. The casing head 11 rests on I the support flange 16 which is mounted at the upper end of the surface pipe 17. A conductor pipe 18 may enclose a portion of the surface pipe 17 and, in a similar way,'a large diameter central column 19 may enclose a portion of the conductor pipe 18. The pipes 17, 18 and 19 extend into the ocean floor. The well head structure 10 is entirely submerged. t

A base member 20 in the form of a supporting flange is mounted between the casing head 11 and the tubing head 12. A central opening 21 in this basemember 20 is aligned with the central passageway 22 in the casing head 11 and the central passageway 23 in the tubing head 12. Thecasing 24, better known as the water string, is provided with a landing mandrel 25 at its upper end and this mandrel has an enlarged portion 26 adapted to seat on a shoulder 27 provided in the casing head 11 near the lower end thereof. A tubing string 28 extends through the interior of the casing 24 and at its upper end is provided with a landing mandrel 29 having an enlarged portion 30 adapted to seat on the shoulder 31 provided in the tubing head 12. The bore 23 in the tubing head 12 and the bore 21 in the base member 29 are large enough to permit axial passage of the landing mandrel 25 therethrough.

The landing mandrels 25 and 29 are provided with portions of reduced diameter 33 and 34 respectively and these reduced diameter portions are engaged by rams 35 and gee-m 36 which are mounted for radial movement on the casing head 11 and tubing head 12 respectively. Rams 35 and 36 maye be conventional tubing head rams such as those shown on page 3602, volume 2 of the Composite Catalog of Oil Field and Pipe Line Equipment, 21st, 1955-56 Edi tion, published by World Oil. This engagement of the rams with the landing mandrels prevents any substantial axial movement of the casing 24 or tubing 28.

The casing head 11 and the tubing head 12 as well as the base member 2% are installed at the time that the surface pipe 17 is set in position. The blowout preventers 13, 14 and 15 are then installed above the tubing head 12. The here through the interior of the blowout preventers is larger than the inside diameter of the surface pipe 17 and, therefore, drill pipe (not shown) may be lowered through the well head equipment in the conventional manner and rotated to drill the oil well. Of course, the drill pipe is operated before the casing 24 or tubing 28 is lowered into position. When the drilling operation is complete the drill pipe (not shown) is withdrawn from the well upwardly through the casing head 11, tubing head 12 and blowout preventers 13, 14 and 15. The casing 24 or waterstring is then lowered through the blowout preventers, tubing head 12 and casing head 11 until the enlarged portion 26 on the landing mandrel 25 engages the shoulder 27. The rams of the blowout preventer 13 are closed and after a successful test of these rams, that portion of the casing above the mandrel 25 is disconnected at the left hand thread 37 at the top of the landing mandrel 25. The blowout preventer rams are then opened and the upper portion of the casing is withdrawn. The upper end 3 38 of the landing mandrel 25 is chamfered to form a bit guile for drilling out cement within the casing and for running successive strings of pipe within the casing, if desired.

The tubing 28 is then lowered through the blowout preventers and through the tubing head 12 and casing head 11 until the enlarged portion 30 of the landing mandrel 29 seats on the shoulder 31. The upper end of the mandrel 29 has a packing assembly 39 which may be manually tightened to form a seal with the tubing head 12 after removal of the blowout preventers 13, 14 and 15, as described below. The packing assembly 39 is tightened by a diver using a wrench on the bolts to clamp the back-up plate 66 thereby laterally displacing the outer portion of the sealing gasket 67 into sealing contact with the bore 23. Shut ofi valves 40 and 41 are mounted in the tubing string 28 above the position of the landing mandrel 29. A remote control dilferential valve 42 is also mounted in this portion of the tubing string.

With the equipment in place as shown in FIGURE :1, the well can be put on production either by swabbing or by circulating. When well fluid has been produced from the well for a period sufiicient to ascertain the characteristics of the well, valve 41 is closed and blowout preventer 13 is disconnected from the upper end of the tubing head 12. The blowout preventers 13, 14 and 15 may then be raised vertically, passing over the tubing string 28 and raised to the surface. The valve 40 is then closed. The upper portion of the tubing string 28 above the difierential valve 42 is then removed and lifted to the surface.

The permanent well head fittings shown in FIGURE 2 are then lowered to the well head structure 10. These well head fittings include nipple 45, swivel joint 46, cross 47, plugs 48 and 49 and piping 50 which extends from the cross 47 to the outlet pipe 51. This outlet pipe 51 passes through the support member 28 and communicates with the shut off valve 52 and adjustable flow bean 53. The hose 54 carries the well fluid away from the well head to any desired location.

Gas under pressure in a suitable container 55 is connected by piping 56 and valve 57 to operate the differential valve 42. A nipple 58a. is. threaded into the base member 29 connected to a shut oft" valve 55.

A large housing or closure 59 is secured to the outer periphery of the support member 21 by means of threaded fasteuings 6t and this housing cooperates with the member 20 to form an enclosure for the tubing head 13. A gasket oi prevents leakage at the joint between the housing 59 and the support member 20?. The valved outlets 58a and 62 function as test ports and circulating outlets for the interior of the enclosure provided by the housing 59.

After the installation and test of the housing 59 the enclosure within the housing may be filled with a noncorrosive liquid such as a soluble oil having a specific gravity approximately the same as sea water.

The well is placed in production by opening valve 52 and the production fluid is removed through the hose 54. The valve 63 opens to the vent line 64 which will serve to indicate any leakage of gas or oil around the well head structure.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

I. The method of completion of an underwater well having a submerged well head structure provided with a blowout preventer, including the steps of: lowering a casting string through the well head structure and blowout preventer to bring a shoulder on the casing string to rest on the well head structure, separating an upper portion of the casing string from a remaining lower portion at a location above said shoulder and below the blowout f prevent-er, removing the upper portion of the casing string, lowering a tubing string through the well head structure and blowout preventer into said remaining portion of the casing string to bring a shoulder on the tubing string to rest on the tubing head, removing the blowout preventer by'raising it axially along the tubing string, removing an upper portion of the tubing string from a remaining portion projecting above the well head structure, and installing an enclosure on the well head structure to encompass said projecting portion of the tubing string.

2. The method of completion of an underwater well having a submerged well head structure provided with a blowout preventer, including the steps of: lowering a casing string through the well head structure and blowout preventer to bring a shoulder on the casing string to rest on the well head structure, separating an upper portion of the casing string from a remaining lower portion at a location above said shoulder and below the blowout preventer, removing the upper portion of the casing string, lowering a valved tubing string through the well head structure and blowout preventer into said remaining portion of the casing string to bring a shoulder on the tubing string to rest on the tubing head, removing the blowout preventer by raising it axially along the tubing string, removing an upper portion of the tubing string above the valve from a remaining portion projecting above the well head structure, and installing an enclosure on the well head structure to encompass said valve and projecting portion of the tubing string.

3. The method of completion of an underwater well having a submerged well head structure provided with a blowout preventer, including the steps of: lowering a casing string through the well head structure and blowout preventer to bring a shoulder on the casing string to rest on the well head structure, separating an upper portion of a lowering a tubing string through the well head structure and blowout preventer into said remaining portion of the casing string to bring a shoulder on the tubing string to rest on the tubing head, securing the casing string and tubing string against upward movement relative to the well head structure, removing the blowout preventer by raising it axially along the tubing string, removing an upper portion of the tubing string from a remaining portion projecting above the well head structure, and installing an enclosure on the well head structure to encompass said projecting portion oi the tubing string.

4. Apparatus for completion of an underwater well, comprising in combination: a submerged well head structure positioned on the ocean bottom and having a casing head with a shoulder provided therein, a tubing head with a shoulder provided therein, an apertured flange member interposed between the casing head and the tubing head, a casing string insertable through the well head structure and having an enlarged portion adapted to rest upon the shoulder of said casing head, a tubing string in sortable through the well head structure and into the casing string and having an enlarged portion adapted to rest upon the shoulder of said tubing head, a valve in the tubing string above the well head structure, means for sealing the annulus between said tubing string and said tubing head, a housing detachably mounted upon the flange member and providing an enclosure containing said valve, and a fluid delivery conduit communicating with said valve and extending exteriorly of said enclosure.

5. Apparatus for completion of an underwater well, comprising in combination: a submerged well head structure positioned on the ocean bottom and having a casing head with a shoulder provided therein, a tubing head, an apertured flange member interposed between the casing head and the tubing head, a casing string insertable through the well head structure and having an enlarged portion adapted to rest upon the shoulder of said casing head, a tubing string insertable through the well head structure and into the casing string and having an enlarged portion adapted to rest upon the shoulder of said tubing head, means on the casing head for preventing longitudinal movement of the casing string, means on the the casing string from a remaining lower portion at a tubing head for preventing longitudinal movement of the tubing string, a valve in the tubing string above the latter said means, means for sealing the annulus between said tubing string and said tubing head, a housing detachably .rnounted upon the flange member and providing an enclosurecontaining said valve, and a fluid delivery conduit communicating with said valve and extending exteriorly of said enclosure.

6. Apparatus for completion of an underwater well, comprising in combination: a submerged well head structure'positioned on the ocean bottom and having a casing head with a shoulder provided therein, a tubing head with a shoulder provided therein, an apertured flange member interposed between the casing head and the tubing head, a casing string insertable through the well head structure and having alanding mandrel resting upon the shoulder of said casing head, a tubing string insertable through the well head structure and into the casing string and having a landing mandrel resting upon the shoulder of said tubing head, retractable sealing rams on the casing head engaging the outer surface of the first said landing mandrel, retractable sealing rams on the tubing head engaging the outer surface of the latter said landing mandrel, a valve in the tubing string above the latter said landing mandrel, 'a housing detachably mounted upon the flange member and providing an enclosure containing said valve, and a fluid delivery conduit communicating with said valve and extending exteriorly of said enclosure.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Grinnel et a1. May 23, 1933 Centeno May 29, 1934 McDonough et a1. May 24, 1938 5 6 Yancey 1 May 6, 1941 Yeatman Apr. 4, 1944 Parks et a1. Aug. 19, 1952 Eckel Sept. 16, 1952 Crowell Feb. 16, 1954 

1. THE METHOD OF COMPLETION OF AN UNDERWATER WELL HAVING A SUBMERGED WELL HEAD STRUCTURE PROVIDED WITH A BLOWOUT PREVENTER, INCLUDING THE STEPS OF: LOWERING A CASTING STRING THROUGH THE WELL HEAD STRUCTURE AND BLOWOUT PREVENTER TO BRING A SHOULDER ON THE CASING STRING TO REST ON THE WELL HEAD STRUCTURE, SEPARATING AN UPPER PORTION OF THE CASING STRING FROM A REMAINING LOWER PORTION AT A LOCATION ABOVE SAID SHOULDER AND BELOW THE BLOWOUT PREVENTER, REMOVING THE UPPER PORTION OF THE CASING STRING, LOWERING A TUBING STRING THROUGH THE WELL HEAD STRUCTURE AND BLOWOUT PREVENTER INTO SAID REMAINING PORTION OF THE CASING STRING TO BRING A SHOULDER ON THE TUBING STRING TO REST ON THE TUBING HEAD, REMOVING THE BLOWOUT PREVENTER BY RAISING IT AXIALLY ALONG THE TUBING STRING, REMOVING AN UPPER PORTION OF THE TUBING STRING FROM A REMAINING PORTION PROJECTING ABOVE THE WELL HEAD STRUCTURE, AND IN- 